01/2012

Hazard tolerability (or acceptability)In assessing the tolerability of various hazards, you must examine the worst credible effect (risk) associated with the hazard. Guidance on this can be found in ICAO Doc 9859 (Safety ManagementManual). The characterisation of the worst credible effect is carried out using the variables of severity and probability (likelihood).Scroll downFrom ICAO Doc 9859: "The process of bringing the safety risks of the consequences of hazards under organizational control starts by assessing the probability that the consequences of hazardsmaterialize during operations aimed at delivery of services. This is known as assessing the safety risk probability. Safety risk probability is defined as the likelihood that an unsafe event or conditionmight occur.The second step in the process of bringing the safety risks of the consequences of hazards under organizational control is the assessment of the severity of the consequences of the hazard if itsdamaging potential materializes during operations aimed at delivery of services. This is known as assessing the safety risk severity.Once the safety risk of the consequences of an unsafe event or condition has been assessed in terms of probability and severity, the third step in the process of bringing the safety risks of theconsequences of the unsafe event or condition under organizational control is the assessment of the tolerability of the consequences of the hazard if its damaging potential materializes duringoperations aimed at delivery of services.This is achieved by combining the safety risk probability and safety risk severity tables into a safety risk assessment matrix."The safety risk matrix, and specific scales used, can be individual to each organisation . However, in the interest of providing guidance to Indian stakeholders and maintaining a consistent approach,the DGCA is providing these two matrices below as a basis for stakeholders' hazard analyses. All stakeholders other than small NSOPs( operating 1‐2 aircraft) should use Matrix 1.Matrix 1 - defaultSeverityMatrix 2 - to be used by small NSOPs onlySeverityCatastProbabilitytrophicHazarrdousMa ajorMin norNegliigibleLead ds toaccide ent orserious s injurySerireductsafety mioustion inmarginsNuisa anceimpact t, or noimp pactFrequent 5 Several times per year, or more 5Occasional 4 Once per year for individual operation 3Remote 3 Very unlikely to occur during lifetime 1Improbable 2 A C EExtremely improbable 1A B C D EProbabilityGreen means Tolerable riskYellow means Tolerable risk if risk mitigations applied, and may require management decision for acceptanceRed means Intolerable under existing circumstances